Homeowners researching mould treatment in Northern Rivers quickly encounter terms like “mould fogging,” “dry fog,” “ULV fogging,” and “antimicrobial misting.” These terms are sometimes used interchangeably by less precise service providers, but they describe different technologies with meaningfully different applications and outcomes. Understanding the distinction helps you ask better questions and ensure you’re getting the right treatment for your property.
Quick answer (BLUF)
“Mould fogging” is a broad term for dispersing antifungal agents as fine airborne particles. “Dry fog” is a specific fogging technology that produces extremely small particles (typically under 10 microns) that remain airborne longer, penetrate into surfaces and cavities more thoroughly, and leave surfaces dry on contact. Both can be effective, but the technology, the product used, and the application context all matter enormously.
What is mould fogging?
Fogging in its general sense involves using a machine to break a liquid antifungal or antimicrobial agent into fine particles and disperse it into the air of a space. The particles settle on surfaces, penetrate into crevices, and create a treated barrier that inhibits mould growth. Fogging can reach areas that manual application, brush, roller, or spray bottle, cannot access: inside wall cavities through penetrations, throughout roof voids, into subfloor spaces, and into the many tiny crevices of a building’s structure.
Different fogging machines produce different particle sizes. The smaller the particle, the longer it remains airborne and the deeper it penetrates into porous surfaces and enclosed spaces. The most common types:
ULV (Ultra Low Volume) cold foggers: These machines use mechanical pressure to produce particles typically in the 5-50 micron range. They’re widely used for pest control and antimicrobial treatments. The particle size means the fog settles on surfaces relatively quickly, effective for open-area surface treatment but less effective for deep cavity penetration.
Thermal foggers: These use heat to vaporise a solution and produce a heavier, denser fog. They’ve largely been superseded for mould work by cold foggers and dry fog technology.
Dry fog systems: True dry fog equipment produces particles under 10 microns, typically in the 5-7 micron range. At this size, the particles behave more like gas than liquid, remaining airborne for extended periods and penetrating into porous materials before settling. They also leave surfaces dry on contact because the particles are small enough that surface tension prevents them from forming a wet layer.
What makes dry fog different?
The critical distinction with dry fog is particle size and penetration. A true dry fog system (often marketed as “dry fog mould treatment”) produces particles small enough to:
- Penetrate into wall cavities through hairline cracks and penetrations
- Permeate porous materials like timber framing, insulation, and plasterboard
- Reach the back faces of surfaces that would be inaccessible to any other treatment method
- Treat the entire air volume of a space thoroughly rather than just surface-level
In the Northern Rivers context, this is particularly relevant for treating homes where mould has penetrated into building structure, post-flood properties in Lismore where wall cavities were saturated, hinterland homes where subfloor and roof void mould has spread through framing, and holiday rental properties where mould has established throughout the building envelope during extended vacant periods.
The product matters as much as the technology
An important point often obscured in marketing material: the antifungal product used in fogging is as important as the fogging technology itself. A dry fog dispersal system using an ineffective product will still produce an ineffective treatment, and a good ULV fogger using an effective, appropriate product can outperform a sophisticated dry fog system using the wrong agent.
Legitimate professional mould fogging and antimicrobial treatment services should be able to tell you:
- What product they are using
- The active ingredient and its registered uses
- The dwell time (how long the product needs to remain in contact with surfaces to be effective)
- The required re-entry period after treatment
- Any surface preparation required beforehand
When fogging is appropriate vs when it isn’t
Fogging is appropriate as:
- A treatment step following manual mould removal and material remediation
- A preventive treatment in at-risk spaces (roof voids, subfloors) before mould establishes
- A standalone treatment for widespread surface mould where the mould has not penetrated into the building structure
- A maintenance treatment for holiday rental properties between seasons
Fogging is not appropriate as:
- A substitute for removing structurally contaminated materials that need to be physically removed
- The only treatment for heavy mould colonisation that has penetrated deep into building materials
- A permanent solution without addressing the underlying moisture source
A common and costly mistake is to fog a home that has deep structural mould and consider the job done. Fogging treats the surfaces and air; it cannot eliminate mould that is deep within a saturated timber stud or rotten insulation batt. If material removal is required, fogging should follow, not replace, that step.
Questions to ask a fogging service provider
- What technology/equipment do you use and what particle size does it produce?
- What product do you use and what is the active ingredient?
- Is the product TGA or EPA registered for mould treatment?
- How long is the dwell time and what is the safe re-entry period?
- Do you conduct a pre-treatment assessment to confirm whether fogging alone is appropriate for my situation, or whether material removal is also needed?
- Do you test air quality before and after treatment to confirm effectiveness?
Professional mould remediation providers with rigorous processes will answer all of these questions clearly and confidently.
FAQs
Is dry fog mould treatment safe for my family?
When conducted by a professional using registered products, and when the appropriate re-entry period has been observed, dry fog treatment is safe. Occupants, particularly children, pregnant women, and those with respiratory conditions, should not be present during treatment and should wait the specified re-entry period before returning. Follow your provider’s specific instructions for the product used.
How long does mould fogging take?
Treatment time varies with the size of the property. A typical residential treatment of a 3-bedroom home takes 1-3 hours of active fogging plus the required dwell time, typically 2-4 hours, though some products specify longer. Total time away from the property is generally 4-8 hours minimum for a full residential treatment.
Can fogging prevent mould coming back?
Quality antimicrobial fogging products include residual agents that continue to inhibit mould growth on treated surfaces for months after application. However, this residual effect is overcome if underlying moisture conditions remain. Fogging is a component of a mould management strategy, not a standalone permanent solution. Regular maintenance treatments, particularly in holiday rental properties or high-humidity environments, extend the protective effect.
Does dry fog damage furniture and belongings?
True dry fog treatment leaves surfaces dry and should not damage fabrics, electronics, or furnishings if used correctly. However, some products may affect certain surfaces, discuss this with your provider before treatment and follow their pre-treatment preparation instructions. Some providers recommend removing or covering certain items as a precaution.